Examples of prior art marine propulsion fuel systems are shown and described in U.S. Pat. Nos. 6,253,742 and 6,390,871, which are both hereby incorporated by reference in their entireties. Some marine propulsion systems, particularly outboard engines, have vented fuel supply modules (FSM), which require special accommodations to ensure that the FSM does not overfill and leak (overflow). These special accommodations may include a lift pump that is controlled by a powertrain control module (PCM) and a float switch within the FSM that controls the lift pump. In these systems, the PCM disables the lift pump when the float switch signals that the FSM is full. The PCM then tallies the amount of fuel consumed by the engine and turns the lift pump on once the total fuel consumed is above a calibrated threshold. The PCM will run the lift pump until the float switch signals that the FSM is full, at which point the PCM will disable the lift pump. The process will repeat during normal operation of the propulsion system. Other marine propulsion systems have unvented fuel supply modules in which the lift pump runs continuously to fill the FSM during normal operation of the propulsion system. Overfilling is usually not a problem for unvented FSMs, as there is no vent from which fluid can leak.